How big can I print my photo? Pixels, PPI and viewing distance
The short answer
Divide the photo's width in pixels by the pixels per inch you need, and multiply by 2.54 for centimetres. A small print held in the hand needs about 300 ppi; a poster seen from a metre or more looks sharp at 100 ppi and fine from two metres at 50 ppi. So a 4,000-pixel phone photo prints sharp to about 100 cm across as a poster, but only 34 cm as a close-up print.
Printers talk about DPI, dots per inch, and photo editors about PPI, pixels per inch. For deciding how big to print, they mean the same thing: how many of the photo’s pixels go into each inch of paper.
The key fact: the right number depends on how far away people stand.
The quick answer
| Photo | Width in pixels | Sharp up close (100 ppi) | Fine from 2 m (50 ppi) |
|---|---|---|---|
| Chat app photo (WhatsApp, Messenger) | ~1,600 | 40 cm | 80 cm |
| Laptop screenshot | ~1,920 | 49 cm | 98 cm |
| 12 MP phone photo | ~4,000 | 100 cm | 2 m |
| 24 MP camera photo | ~6,000 | 150 cm | 3 m |
“Up close” here means a poster seen from about a metre — across a room, not in your hands.
The formula
Print width (cm) = pixels ÷ ppi × 2.54
A 4,000-pixel photo at 100 ppi: 4,000 ÷ 100 × 2.54 = 101.6 cm.
Or backwards, to find the pixels you need: pixels = width in cm ÷ 2.54 × ppi.
Why distance changes everything
Your eye can only resolve so much detail at a given distance. Stand back twice as far and you need roughly half the pixels per inch to see the same sharpness.
| Viewed from | Pixels per inch that look sharp |
|---|---|
| In the hand (30 cm) | about 300 |
| Desk or shelf (60 cm) | about 150 |
| Across a room (1 m+) | about 100 |
| Down a corridor (2 m+) | about 50 |
| A billboard | under 20 |
This is why the “always 300 DPI” rule is right for a photo album and wrong for a wall poster. At 300 ppi, a 4,000-pixel photo is only 34 cm wide — far smaller than it needs to be.
Find your photo’s pixel size
- iPhone: open the photo in Photos and swipe up. The size shows as, for example, 12 MP · 4032 × 3024.
- Android: open it in Google Photos, tap the three dots or swipe up for details.
- Windows: right-click the file → Properties → Details.
- Mac: open it in Preview → Tools → Show Inspector.
The first number is the width in pixels.
Why the same photo prints small from WhatsApp
Chat apps shrink photos to save data, usually to about 1,600 pixels on the long side. A photo that left the camera at 4,000 pixels arrives at 1,600: sharp as a poster only to about 40 cm. Always print from the original. On WhatsApp, sending a photo “as a document” keeps it full size.
What about upscaling?
Making a small photo larger does not add detail; it stretches what is there. AI upscalers can invent plausible detail and sometimes look convincing on faces and landscapes, but it is a guess. Start from the biggest original you can find.
Let the tool do the sums
The giant photo poster page and the poster maker work this out as you change the size. Pick a width and they tell you whether the picture will be sharp, fine from a distance or blurry — before you spend any ink. Then they split it into A4 or Letter sheets to print at home. For the printing and gluing, see how to print a large poster on A4.
- Printing
- Photos
